Sox17 regulates liver lipid metabolism and adaptation to fasting

Culex quinquefasciatus Resistant to the Binary Toxin from Lysinibacillus sphaericus Displays a Consistent Downregulation of Pantetheinase Transcripts

Culex quinquefasciatus resistance to the binary (Bin) toxin, the major larvicidal component from Lysinibacillus sphaericus, is associated with mutations in the cqm1 gene, encoding the Bin-toxin receptor. Downregulation of the cqm1 transcript was found in the transcriptome of larvae resistant to the L. sphaericus IAB59 strain, which produces both the Bin toxin and a second binary toxin, Cry48Aa/Cry49Aa. Here, we investigated the transcription profiles of two other mosquito colonies having Bin resistance only. These confirmed the cqm1 downregulation and identified transcripts encoding the enzyme pantetheinase as the most downregulated mRNAs in both resistant colonies. Further quantification of these transcripts reinforced their strong downregulation in Bin-resistant larvae. Multiple genes were found encoding this enzyme in Cx. quinquefasciatus and a recombinant pantetheinase was then expressed in Escherichia coli and Sf9 cells, with its presence assessed in the midgut brush border membrane of susceptible larvae. The pantetheinase was expressed as a ~70 kDa protein, potentially membrane-bound, which does not seem to be significantly targeted by glycosylation. This is the first pantetheinase characterization in mosquitoes, and its remarkable downregulation might reflect features impacted by co-selection with the Bin-resistant phenotype or potential roles in the Bin-toxin mode of action that deserve to be investigated.

TCDD dysregulation of lncRNA expression, liver zonation and intercellular communication across the liver lobule

The persistent environmental aryl hydrocarbon receptor agonist and hepatotoxin TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) induces hepatic lipid accumulation (steatosis), inflammation (steatohepatitis) and fibrosis. Thousands of liver-expressed, nuclear-localized lncRNAs with regulatory potential have been identified; however, their roles in TCDD-induced hepatoxicity and liver disease are unknown. We analyzed single nucleus (sn)RNA-seq data from control and subchronic (4 wk) TCDD-exposed mouse liver to determine liver cell-type specificity, zonation and differential expression profiles for thousands of lncRNAs. TCDD dysregulated >4000 of these lncRNAs in one or more liver cell types, including 684 lncRNAs specifically dysregulated in liver non-parenchymal cells. Trajectory inference analysis revealed major disruption by TCDD of hepatocyte zonation, affecting >800 genes, including 121 lncRNAs, with strong enrichment for lipid metabolism genes. TCDD also dysregulated expression of >200 transcription factors, including 19 Nuclear Receptors, most notably in hepatocytes and Kupffer cells. TCDD-induced changes in cell-cell communication patterns included marked decreases in EGF signaling from hepatocytes to non-parenchymal cells and increases in extracellular matrix-receptor interactions central to liver fibrosis. Gene regulatory networks constructed from the snRNA-seq data identified TCDD-exposed liver network-essential lncRNA regulators linked to functions such as fatty acid metabolic process, peroxisome and xenobiotic metabolism. Networks were validated by the striking enrichments that predicted regulatory lncRNAs showed for specific biological pathways. These findings highlight the power of snRNA-seq to discover functional roles for many xenobiotic-responsive lncRNAs in both hepatocytes and liver non-parenchymal cells and to elucidate novel aspects of foreign chemical-induced hepatotoxicity and liver disease, including dysregulation of intercellular communication within the liver lobule.

TCDD dysregulation of lncRNA expression, liver zonation and intercellular communication across the liver lobule

The persistent environmental aryl hydrocarbon receptor agonist and hepatotoxin TCDD (2,3,7,8-tetrachlorodibenzo- p -dioxin) induces hepatic lipid accumulation (steatosis), inflammation (steatohepatitis) and fibrosis. Thousands of liver-expressed, nuclear-localized lncRNAs with regulatory potential have been identified; however, their roles in TCDD-induced hepatoxicity and liver disease are unknown. We analyzed single nucleus (sn)RNA-seq data from control and chronic TCDD-exposed mouse liver to determine liver cell-type specificity, zonation and differential expression profiles for thousands of IncRNAs. TCDD dysregulated >4,000 of these lncRNAs in one or more liver cell types, including 684 lncRNAs specifically dysregulated in liver non-parenchymal cells. Trajectory inference analysis revealed major disruption by TCDD of hepatocyte zonation, affecting >800 genes, including 121 IncRNAs, with strong enrichment for lipid metabolism genes. TCDD also dysregulated expression of >200 transcription factors, including 19 Nuclear Receptors, most notably in hepatocytes and Kupffer cells. TCDD-induced changes in cellâ€"cell communication patterns included marked decreases in EGF signaling from hepatocytes to non-parenchymal cells and increases in extracellular matrix-receptor interactions central to liver fibrosis. Gene regulatory networks constructed from the snRNA-seq data identified TCDD-exposed liver network-essential lncRNA regulators linked to functions such as fatty acid metabolic process, peroxisome and xenobiotic metabolic. Networks were validated by the striking enrichments that predicted regulatory IncRNAs showed for specific biological pathways. These findings highlight the power of snRNA-seq to discover functional roles for many xenobiotic-responsive lncRNAs in both hepatocytes and liver non-parenchymal cells and to elucidate novel aspects of foreign chemical-induced hepatotoxicity and liver disease, including dysregulation of intercellular communication within the liver lobule.

A mutation in the SAA1 promoter causes hereditary amyloid A amyloidosis

Amyloid A amyloidosis is a serious clinical condition resulting from the systemic deposition of amyloid A originating from serum amyloid A proteins with the kidneys being the most commonly and earliest affected organ. Previously described amyloid A amyloidosis is linked to increased production and deposition of serum amyloid A proteins secondary to inflammatory conditions arising from infectious, metabolic, or genetic causes. Here we describe a family with primary amyloid A amyloidosis due to a chr11:18287683 T>C (human genome version19) mutation in the SAA1 promoter linked to the amyloidogenic SAA1.1 haplotype. This condition leads to a doubling of the basal SAA1 promoter activity and sustained elevation of serum amyloid A levels that segregated in an autosomal dominant pattern in 12 genetically affected and in none of six genetically unaffected relatives, yielding a statistically significant logarithm of odds (LOD) score over 5. Affected individuals developed proteinuria, chronic kidney disease and systemic deposition of amyloid composed specifically of the SAA1.1 isoform. Tocilizumab (a monoclonal antibody against the interleukin-6 receptor) had a beneficial effect when prescribed early in the disease course. Idiopathic forms represent a significant and increasing proportion (15-20%) of all diagnosed cases of amyloid A amyloidosis. Thus, genetic screening of the SAA1 promoter should be pursued in individuals with amyloid A amyloidosis and no systemic inflammation, especially if there is a positive family history.

Hepatic transcriptional responses to fasting and feeding

Mammals undergo regular cycles of fasting and feeding that engage dynamic transcriptional responses in metabolic tissues. Here we review advances in our understanding of the gene regulatory networks that contribute to hepatic responses to fasting and feeding. The advent of sequencing and -omics techniques have begun to facilitate a holistic understanding of the transcriptional landscape and its plasticity. We highlight transcription factors, their cofactors, and the pathways that they impact. We also discuss physiological factors that impinge on these responses, including circadian rhythms and sex differences. Finally, we review how dietary modifications modulate hepatic gene expression programs.

Fasting Increases Iron Export by Modulating Ferroportin 1 Expression Through the Ghrelin/GHSR1α/MAPK Pathway in the Liver

The liver is contributed to maintaining body iron homeostasis and controlling of body adaptation to fasting. Although previous studies implied a negative relationship between iron and ghrelin in both mice and humans, it remains to be explored whether fasting or ghrelin has a functional effect on iron homeostasis in the liver. In this study, we examined the roles of fasting and ghrelin in modulating the protein expression of Fpn1, transferrin receptor 1 (TfR1), and ferritin light chain (Ft-L), as well as the mRNA expression of ghrelin, hepcidin, ghrelin O-acyltransferase (GOAT), and growth hormone secretagogue receptor 1 alpha (GHSR1α) in mouse liver and cultured hepatocytes. Our in vivo results suggested that fasting significantly upregulated the mRNA expression of ghrelin, GOAT, and GHSR1α, as well as the protein levels of ghrelin, Fpn1, and Ft-L, but not TfR1, in mouse liver. Interestingly, mRNA expression of hepcidin did not change significantly after fasting. Meanwhile, in cultured hepatocytes, ghrelin significantly increased the protein expression of Fpn1 but not Ft-L and TfR1 and significantly enhanced ERK phosphorylation. Furthermore, the pretreatment of cultured hepatocytes with either a pERK inhibitor or a GHSR1α antagonist abolished the effects of ghrelin on Fpn1 expression and ERK phosphorylation. Our findings confirmed that fasting increases iron export in the liver by upregulating Fpn1 expression through the ghrelin/GHSR1α/MAPK signaling pathway.

Dioxin-like and non-dioxin-like PCBs differentially regulate the hepatic proteome and modify diet-induced nonalcoholic fatty liver disease severity

Polychlorinated biphenyls (PCBs) are persistent organic pollutants associated with metabolic disruption and non-alcoholic fatty liver disease (NAFLD). Based on their ability to activate the aryl hydrocarbon receptor (AhR), PCBs are subdivided into two classes: dioxin-like (DL) and non-dioxin-like (NDL) PCBs. Previously, we demonstrated that NDL PCBs compromised the liver to promote more severe diet-induced NAFLD. Here, the hepatic effects and potential mechanisms (by untargeted liver proteomics) of DL PCBs, NDL PCBs or co-exposure to both in diet-induced NAFLD are investigated. Male C57Bl/6 mice were fed a 42% fat diet and exposed to vehicle control; Aroclor1260 (20 mg/kg, NDL PCB mixture); PCB126 (20 μg/kg, DL PCB congener); or a mixture of Aroclor1260 (20 mg/kg)+PCB126 (20 μg/kg) for 12 weeks. Each exposure was associated with a distinct hepatic proteome. Phenotypic and proteomic analyses revealed increased hepatic inflammation and phosphoprotein signaling disruption by Aroclor1260. PCB126 decreased hepatic inflammation and fibrosis at the molecular level; while altering cytoskeletal remodeling, metal homeostasis, and intermediary/xenobiotic metabolism. PCB126 attenuated Aroclor1260-induced hepatic inflammation but increased hepatic free fatty acids in the co-exposure group. Aroclor1260+PCB126 exposure was strongly associated with multiple epigenetic processes, and these could potentially explain the observed non-additive effects of the exposures on the hepatic proteome. Taken together, the results demonstrated that PCB exposures differentially regulated the hepatic proteome and the histologic severity of diet-induced NAFLD. Future research is warranted to determine the AhR-dependence of the observed effects including metal homeostasis and the epigenetic regulation of gene expression.

ZNF263 is a transcriptional regulator of heparin and heparan sulfate biosynthesis

Heparin is the most widely prescribed biopharmaceutical in production globally. Its potent anticoagulant activity and safety makes it the drug of choice for preventing deep vein thrombosis and pulmonary embolism. In 2008, adulterated material was introduced into the heparin supply chain, resulting in several hundred deaths and demonstrating the need for alternate sources of heparin. Heparin is a fractionated form of heparan sulfate derived from animal sources, predominantly from connective tissue mast cells in pig mucosa. While the enzymes involved in heparin biosynthesis are identical to those for heparan sulfate, the factors regulating these enzymes are not understood. Examination of the promoter regions of all genes involved in heparin/heparan sulfate assembly uncovered a transcription factor-binding motif for ZNF263, a C2H2 zinc finger protein. CRISPR-mediated targeting and siRNA knockdown of ZNF263 in mammalian cell lines and human primary cells led to dramatically increased expression levels of HS3ST1, a key enzyme involved in imparting anticoagulant activity to heparin, and HS3ST3A1, another glucosaminyl 3-O-sulfotransferase expressed in cells. Enhanced 3-O-sulfation increased binding to antithrombin, which enhanced Factor Xa inhibition, and binding of neuropilin-1. Analysis of transcriptomics data showed distinctively low expression of ZNF263 in mast cells compared with other (non-heparin-producing) immune cells. These findings demonstrate a novel regulatory factor in heparan sulfate modification that could further advance the possibility of bioengineering anticoagulant heparin in cultured cells.

TFAP2 transcription factors are regulators of lipid droplet biogenesis

How trafficking pathways and organelle abundance adapt in response to metabolic and physiological changes is still mysterious, although a few transcriptional regulators of organellar biogenesis have been identified in recent years. We previously found that the Wnt signaling directly controls lipid droplet formation, linking the cell storage capacity to the established functions of Wnt in development and differentiation. In the present paper, we report that Wnt-induced lipid droplet biogenesis does not depend on the canonical TCF/LEF transcription factors. Instead, we find that TFAP2 family members mediate the pro-lipid droplet signal induced by Wnt3a, leading to the notion that the TFAP2 transcription factor may function as a 'master' regulator of lipid droplet biogenesis.

Comparison of the transcriptomic profile of hepatic human induced pluripotent stem like cells cultured in plates and in a 3D microscale dynamic environment

We have compared the transcriptomic profiles of human induced pluripotent stem cells after their differentiation in hepatocytes like cells in plates and microfluidic biochips. The biochips provided a 3D and dynamic support during the cell differentiation when compared to the 2D static cultures in plates. The microarray have demonstrated the up regulation of important pathway related to liver development and maturation during the culture in biochips. Furthermore, the results of the transcriptomic profile, coupled with immunostaining, and RTqPCR analysis have shown typical biomarkers illustrating the presence of responders of biliary like cells, hepatocytes like cells, and endothelial like cells. However, the overall tissue still presented characteristic of immature and foetal patterns. Nevertheless, the biochip culture provided a specific micro-environment in which a complex multicellular differentiation toward liver could be oriented.

Mouse Sox17 haploinsufficiency leads to female subfertility due to impaired implantation

Embryonic implantation comprises a dynamic and complicated series of events, which takes place only when the maternal uterine endometrium is in a receptive state. Blastocysts reaching the uterus communicate with the uterine endometrium to implant within a narrow time window. Interplay among various signalling molecules and transcription factors under the control of ovarian hormones is necessary for successful establishment of pregnancy. However, the molecular mechanisms that allow embryonic implantation in the receptive endometrium are still largely unknown. Here, we show that Sry-related HMG box gene-17 (Sox17) heterozygous mutant female mice exhibit subfertility due to implantation failure. Sox17 was expressed in the oviduct, uterine luminal epithelium, and blood vessels. Sox17 heterozygosity caused no appreciable defects in ovulation, fertilisation, blastocyst formation, and gross morphology of the oviduct and uterus. Another group F Sox transcription factor, Sox7, was also expressed in the uterine luminal and glandular epithelium relatively weakly. Despite uterine Sox7 expression, a significant reduction in the number of implantation sites was observed in Sox17 heterozygous mutant females due to haploinsufficiency. Our findings revealed a novel role of Sox17 in uterine receptivity to embryo implantation.

MiR-122 targets the vanin 1 gene to regulate its expression in chickens

As the most abundant microRNA (miRNA) in the liver, miR-122 plays important roles in the growth and development of liver, lipid metabolism, and liver diseases. Vanin 1 (VNN1) plays an important role in hepatic lipid metabolism, and VNN1 may serve as a potential therapeutic target for the treatment of metabolic diseases caused by overactivated gluconeogenesis. In our previous RNA-seq study, we found the expression of VNN1 increased significantly when the expression of miR-122 (gga-miR-122-5p) was knocked down in primary chicken hepatocytes. In this study, we verified this result by real-time qRT-PCR, and we also found that the chicken VNN1 was highly expressed in the liver. By bioinformatics analyses, we found the 3'UTR of VNN1 contained sequences completely complementary to the nucleotides 1 to 8 of miR-122. Co-transfection and dual-luciferase reporter assays showed that overexpression of miR-122 decreased the expression of luciferase reporter gene linked to the 3'UTR of chicken VNN1 in the Chinese hamster ovary cells (P<0.01), and the decrease was further demonstrated to be dependent on the predicted miR-122 binding sites by site mutation analyses. These results further support miR-122 as a negative regulator of VNN1 expression in chicken hepatocytes. Overall, this study suggests that miR-122 might play an important role in lipid metabolism in the chicken liver by negatively regulating the expression of the VNN1 gene.

Serum pantetheinase/vanin levels regulate erythrocyte homeostasis and severity of malaria

Tissue pantetheinase, encoded by the VNN1 gene, regulates response to stress, and previous studies have shown that VNN genes contribute to the susceptibility to malaria. Herein, we evaluated the role of pantetheinase on erythrocyte homeostasis and on the development of malaria in patients and in a new mouse model of pantetheinase insufficiency. Patients with cerebral malaria have significantly reduced levels of serum pantetheinase activity (PA). In mouse, we show that a reduction in serum PA predisposes to severe malaria, including cerebral malaria and severe anemia. Therefore, scoring pantetheinase in serum may serve as a severity marker in malaria infection. This disease triggers an acute stress in erythrocytes, which enhances cytoadherence and hemolysis. We speculated that serum pantetheinase might contribute to erythrocyte resistance to stress under homeostatic conditions. We show that mutant mice with a reduced serum PA are anemic and prone to phenylhydrazine-induced anemia. A cytofluorometric and spectroscopic analysis documented an increased frequency of erythrocytes with an autofluorescent aging phenotype. This is associated with an enhanced oxidative stress and shear stress-induced hemolysis. Red blood cell transfer and bone marrow chimera experiments show that the aging phenotype is not cell intrinsic but conferred by the environment, leading to a shortening of red blood cell half-life. Therefore, serum pantetheinase level regulates erythrocyte life span and modulates the risk of developing complicated malaria.